Increase in concanavalin A cap formation on lymphoma cells following interaction with inactive influenza viruses.

Binding of the lectin Con A to its ligand on the cell surface of normal circulating lymphocytes induces capping in 28-32% of these cells. This Con A cap formation is markedly decreased in malignant cells from the human hematopoietic system. Among others, the human lymphoma Daudi cell line exhibit a cap formation with Con A in only 5-10% of the cells. In this study, we found that inactivated influenza viruses induced changes in the cell surface membrane of Daudi cells resulting in an increased percentage of Con A cap forming cells (30-40%). This phenomenon occurred independently of viral replication and was initiated by adsorption of inactivated viral particles or isolated hemagglutinin and neuraminidase viral glycoproteins. This phenomenon may be due to the binding of Con A molecules to viral receptors and to cell receptors leading to crosslinking of Con A receptors that will induce their mobility and the formation of a cap. Alternatively, experiments performed with cytochalasin B and colchicine suggest that the viral interaction with the cell membrane may have induced changes in the cytoskeleton at the level of microtubules. These changes induced increased lateral movement of the Con A receptors resulting into formation of a cap.